Police have located a 60-year-old theft report from the day a Renoir painting disappeared from the Baltimore Museum of Art that matches the description of an artwork that sold for $7 recently at a flea market. Now an art theft expert says the museum has a strong case to get it back.

Baltimore police on Friday uncovered the report from Nov. 17, 1951. The museum on Thursday said it also found a record in its library that the painting was stolen. The police report noted there was no evidence of forced entry at the museum and that the painting was valued then at $2,500.

According to the report, James N. Foster Jr., an executive assistant at the museum, reported that “some time between 6 p.m. Nov. 16 and 1 p.m. this date (Nov. 17) someone stole the following painting.”

The brief police report notes the 5½-by-9-inch piece, “On the Shore of the Seine,” was painted by Pierre-Auguste Renoir. It describes “a river scene in pink and blue.” No other items were reported stolen.

Six decades later, a Virginia woman said she bought the painting at a West Virginia flea market in 2010. She kept it in storage for nearly two years — thinking it must be fake — and then decided to have it examined by an auction house in Alexandria.

The Potomack Co. verified it was Renoir’s “Paysage Bords de Seine,” which translates to Banks of the River Seine. The auction house said it checked a worldwide registry of stolen artwork in July, and the Renoir piece had never been reported stolen or missing.

The painting was to be sold at auction for the woman on Saturday, and it was expected to fetch at least $75,000.

The auction was postponed this week after a Washington Post reporter first found evidence the painting had been on loan to the museum from 1937 until 1951.

An expert on art thefts told the Associated Press the museum likely has a strong case to reclaim the painting. Robert Wittman, a former FBI investigator of national art thefts, said the artwork’s dimensions and composition are key in matching it to a stolen piece.

“I just figured it would be a matter of time before somebody made a claim because those things just don’t disappear,” Mr. Wittman said of the Renoir found in a box of trinkets.

If there’s a legal dispute over ownership of the painting, it would likely be a civil, not criminal, dispute, Mr. Wittman said.

The museum’s insurance company from 1951 also might be able to make a claim, though the museum had not located insurance records to identify the company.

Museum officials were combing through paper records Friday to learn more about the theft. So far, they have found a record documenting the museum had borrowed the painting from art patron Saidie A. May, who donated many other works to the museum.

The painting was on exhibit at the time it was stolen, said museum spokeswoman Anne Mannix. It’s listed in a catalog for the 1951 exhibit, “From Ingres to Gauguin: French 19th Century Paintings Owned in Maryland.”

Susan Helen Adler, a great-niece of May and an art teacher, has written a book about the life of her art collecting ancestor. She said there is no doubt May intended for the Renoir to stay at the museum permanently.

“In her will, every piece of art that had been in the museum was to stay in the museum,” Ms. Adler said.

Art records indicate the painting was sold in 1926 by the Bernheium-Jeune gallery in Paris to American lawyer Herbert L. May. The family believes he gave it to his wife, Saidie May, as a gift before they divorced.

Saidie May began loaning her extensive collection to about six U.S. museums and each year could take a portion of the value off her taxes. Her sister, Blanche Adler, lived in Baltimore and was a trustee at the Baltimore Museum of Art.

“I hope that they figure out how it was taken because it just seems odd,” said Susan Helen Adler. “It is a small piece of art. Maybe that’s how the people were able to get it out of the museum.”

Before the police report was found, the museum’s loan record was its only documentation of the painting being stolen. The card noted the museum had collected $2,500 from its insurance company after the loss.

“All the way up through 1951 you have it listed in the [museum] card file. Then it disappears … and the thing shows up in somebody’s garage,” said Mr. Wittman, the former FBI agent. “It’s remarkable that the museum would still have that catalog card. That’s fabulous.”

The FBI has confirmed it’s investigating. Mr. Wittman, who retired in 2008, said investigators would likely go back to the flea market and try to identify who sold it to try to determine where the piece came from.